The overall objective of this study is to compare two strategies for the management of atrial fibrillation. The first strategy involves antiarrhythmic drugs to be administered to maintain normal sinus rhythm, if possible. In the second strategy, a different group of drugs and/or catheter ablation will be used for the purpose of heart rate control only. The primary endpoint by which these two strategies will be compared is total mortality. This study will enroll approximately 5,300 patients who will each be randomized to one of the two management strategies. Details of the study design include patient entry criteria, randomization procedures, and analyses which will be incorporated into a protocol developed by the contractor with selected consultants, and the National Heart, Lung, and Blood Institute (NHLBI) staff.